LC/TOFMS and UPLC-MS/MS Methods for the Analysis of Perfluorooctanesulfonate (PFOS) and the Reduction of Matrix Interference in Complex Biological Matrices.

摘要

Perfluorinated compounds (PFCs) comprise a class of anthropogenic compounds that are regularly detected in biological and environmental samples globally. PFCs are used in a multitude of commercial and industrial processes and products. Perfluorooctane sulfonate (PFOS) is one of the PFCs that are frequently detected in biological and environmental samples. Many studies that have investigated PFOS in marine mammals, avian species, aquatic species, and human serum have been based on LC-MS/MS analysis using a single multiple-reaction-monitoring (MRM) transition (499 m/z - > 80 m/z) for quantitation. A recent publication (1) reported a common matrix interferent (taurodeoxycholate) that can complicate PFOS quantitation because it undergoes the same transition (499 m/z - > 80 m/z) and it tends to coelute with PFOS, leading to a positive bias. The comparison of UPLC/MS/MS and LC/TOFMS for the chromatographic separation and quantitation of PFOS in complex biological matrices is shown. A Waters Aquity UPLC interfaced with a Quattro Premier XE triple quadrupole mass spectrometer and an Agilent 1100 HPLC interfaced with an Agilent Series 6000 TOF mass spectrometer were used for sample analysis. Acquisition files containing quantitation and confirmation ions for each analyte were generated for the triple quadrupole mass spectrometer using values from individual compound optimization. Exact masses and mass defects for each analyte and optimum fragmentation voltage was determined using the TOF instrument. The biological matrices evaluated in this work include whole-fish homogenates, fish livers, avian eggs and human serum. This work describes an UPLC/MS/MS method for the complete separation of PFOS from known impurities for more accurate quantitation. Most analytical laboratories rely on triple quadrupole MS/MS instruments as the primary means of PFC quantitation. But without careful attention to the appropriate MRMs, PFOS quantitation can be questionable. We have found several common matrix impurities that may co-elute with PFOS which also give the 499 m/z - > 80 m/z transition but can be identified with the addition of 2 unique MRMs. This work specifically shows why multiple MRMs are necessary for the proper quantitation and verification of PFOS in complex biological and environmental matrices. To further help avoid this potential problem, an SPE method has been developed for removal of these known matrix impurities from complex biological samples. LC/TOFMS is another approach for the analysis of PFCs and it is particularly useful for the identification and quantitation of PFOS in complex biological matrices. Accurate mass determination (+- 10 ppm) provided by TOFMS allows for the separation of PFOS from potentially co-eluting matrix impurities that have very similar molecular weights and mass transitions. If combined with good chromatographic separation, an LC/TOFMS approach can provide superior selectivity in identification and quantitation of PFOS isolated from complex biological matrices in comparison to standard triple quadrupole MS/MS techniques. Typical MS/MS procedures only provide +/- 0.5 amu accuracy through the first quadrupole when parent - > daughter transitions are produced. PFOS (498.65) and a group of common biological matrix impurities (cholic acids at 498.35) are close enough in molecular weight that most triple quadrupole MS/MS systems to fail to distinguish between these two types of compounds. In addition, the primary transition for both is the loss of a sulfonate group (79.90 m/z). However, with TOFMS analysis, the PFOS (498.9302 m/z) is significantly different from the cholic acids (498.2895 m/z) to be easily separated due to molecular weight alone.